自底向上构建高效BVH的研究

光线追踪中,加速结构对于减少光线与几何体求交的计算量起到了不可或缺的作用,找到一种高效的加速结构仍然是本领域的研究热点之一.传统的加速结构如BVH,都是自顶向下的构建方式,由于其本身的限制,构造出的加速结构往往不是最优的.为了改进自顶向下的缺陷,提出了一种自底向上BVH的构建方式,它使用了BVH和空间划分的混合结构,并引入了一种改进的表面积启发代价函数和多个构建参数来优化最后的构建结果.最后实验表明,此文中提出的方式比传统的BVH与KD-Trees有更好的加速效果,可以实现对前两者5%-10%的提速.最后,文中还给出了一些加速方案来减少构建时间.     

Interactive tree modeling and deformation with collision detection and avoidance

We present an interactive tree modeling and deformation system that supports an efficient collision detection and avoidance using a bounding volume hierarchy of sweep surfaces. Starting with conventional tree models (given as meshes), we convert them into sweep surfaces and deform their branches interactively while detecting and avoiding collisions with many other branches. Multiple tree models (sharing the same topology) can be generated with great ease using this sweep‐based approach, and they can serve as a basis for the generation of a multiparameter family of trees. We demonstrate the effectiveness of our approach in an automatic generation of similar trees, the colonization of trees to form a forest, and the tree growth, aging, and withering simulations. Copyright © 2015 John Wiley & Sons, Ltd.     

基于BVH驱动的OGRE骨骼动画*

OGRE游戏引擎中的角色动画将模型与骨骼文件进行映射。若想在不借助第三方建模软件重新制作模型和动画的基础上更改现有模型的动作,获取与模型匹配的骨骼数据成为一个难题。提出了一种将标准BVH动作文件解析为XML文件的方法,生成与OGRE模型匹配的骨骼文件,将来源广泛的BVH文件作为动作数据,极大地丰富了OGRE角色动画。实验结果证明,转换后的BVH可以与OGRE中的模型融合起来,从而驱动模型。     

基于运动传感器的远程健康监护系统研究

摘要设计了一种基于惯性测量单元((IMU Inertial Measurement Unit)的远程健康监护系统。首先采集固定在人体上的4个惯性测量单元的加速度、地磁和角速度数据,然后对数据采用卡尔曼滤波器进行融合,最后将融合后的姿态数据写入I3VH文件后传输到远程医护人员的计算机,以便医护人员对病人进行监护。实验结果表明,系统能实时准确地采集到人体的姿态数据,并能实时地再现人体的动作。     

基于紧身衣的人体动画研究

传统人体动画技术计算量大,缺乏真实感,制作成本昂贵.为此,提出了一种基于紧身衣和相机定标的新的人体动画技术.将身穿紧身衣模特的运动拍摄成视频后,可在图像序列中自动跟踪人体关节信息,并建立透视投影下的三维人体运动骨架序列,最终通过自动生成BVH(biovision hierarchy)文件与当今流行的Poser, 3DMax等人体动画制作软件接口,将模特的运动信息赋予新的角色.该方法具有运动信息来源广泛、高效、制作成本低等特点,而且产生的人体运动非常真实.这不仅将动画师从枯燥的工作中解放出来,而且也可用于家     

基于着色算法的并行碰撞检测算法*

提出了一种基于着色算法的并行碰撞检测算法,利用AABB包围盒较好的紧密性和包围球计算简单的优点以及并行算法中的分治策略构建物体的混合包围体层次(S-AABB);然后采用破对称技术中的典型算法——着色算法,将每棵任务树编码,以产生各不相同的类别,并将不同的类别指派到不同的并行机,在并行机上采用多线程技术执行相同的类别的任务树的遍历,来检测是否有碰撞发生。实验结果表明,与现有的经典的I-COLLIDE等算法相比,该算法在效率、精确性方面具有明显优势,能够满足交互式复杂虚拟环境的实时性和精确性的要求。     

Massively Parallel Hierarchical Scene Processing with Applications in Rendering

We present a novel method for massively parallel hierarchical scene processing on the GPU, which is based on sequential decomposition of the given hierarchical algorithm into small functional blocks. The computation is fully managed by the GPU using a specialized task pool which facilitates synchronization and communication of processing units. We present two applications of the proposed approach: construction of the bounding volume hierarchies and collision detection based on divide‐and‐conquer ray tracing. The results indicate that using our approach we achieve high utilization of the GPU even for complex hierarchical problems which pose a challenge for massive parallelization. The results indicate that using our approach we achieve high utilization of the GPU even for complex hierarchical problems which pose a challenge for massive parallelization.     

BVH文件驱动三维人体动画的实现

三维人体动画是虚拟现实技术中的一大难点。提出一种利用BVH(BiovisionHierarchy)文件驱动三维人体动画的方法,并采用OpenGL(Open Graphics Library)绘制三维人体,最后给出了实现结果。由于采用OpenGL绘制复杂的人体模型需要保存动画中的顶点和面片的信息,这将大大增加三维人体动画的计算量,所以使用简单的圆柱和圆球来绘制三维人体,以便能快速准确地模拟三维人体动画。结果表明可以实现比较逼真的三维人体动画。     

线索化包围盒层次结构的并行创建算法

针对光线跟踪的场景加速结构创建问题,提出一种线索化包围盒层次结构(BVH)的图形处理器并行创建算法。算法完全以宽度优先搜索顺序创建包围盒结点,包括大结点和小结点两个创建过程,其分别并行化面片运算和结点运算,解决了创建上层结点时缺乏数据并行度的问题。算法通过3个独立步骤实现BVH的宽度优先到深度优先存储结构变换以及包围盒结点的线索化操作。实验结果表明,本文算法的创建速度高于已有的非线索化BVH创建算法。     

Fast Insertion‐Based Optimization of Bounding Volume Hierarchies

We present an algorithm for fast optimization of bounding volume hierarchies (BVH) for efficient ray tracing. We perform selective updates of the hierarchy driven by the cost model derived from the surface area heuristic. In each step, the algorithm updates a fraction of the hierarchy nodes to minimize the overall hierarchy cost. The updates are realized by simple operations on the tree nodes: removal, search and insertion. Our method can quickly reduce the cost of the hierarchy constructed by the traditional techniques, such as the surface area heuristic. We evaluate the properties of the proposed method on fourteen test scenes of different complexity including individual objects and architectural scenes. The results show that our method can improve a BVH initially constructed with the surface area heuristic by up to 27% and a BVH constructed with the spatial median split by up to 88%.